1. Field of the Invention
The present invention relates to piston-mounted devices for the generation of electrical power during reciprocation of the piston; particularly, to such a device which allow a powering of a telemetry package mounted on an engine piston for obtaining data concerning conditions at the piston during engine operation.
2. Description of Related Art
All engine manufacturers require data from pistons of operating engines, such as temperatures, strains, etc.; but, doing so has been limited by problems in transferring signals frown the reciprocating components, as well as the need to supply sufficient electrical power to activate transducers and circuits of telemetry systems without the temperature and test duration limitations of batteries.
At present, extensive mechanical modifications must be made to engines in order to incorporate short-lived "grasshopper" links for transferring signals by wire to the piston. Use of telemetry is severely limited by battery life or by the need to incorporate complex inductive power transfer systems requiring significant engine-specific modifications. A system used by Southwest Research Institute uses a ballistic core moving freely within a coil to generate electrical power for telemetry purposes. However, this device does not begin to operate until high engine speed, and does not provide sufficient power for general use, e.g., sufficient power is produced to enable only piston temperatures to be measured.
Numerous devices exist which use a piston arrangement for the generation of power by changing the magnetic flux in a coil. For example, U.S. Pat. No. 3,206,609 to Dawes discloses a reciprocating magnet located in a piston of a two-cycle engine, an alternating current being generated in a transformer coil surrounding the cylinder due to the moving magnetic field created by the moving piston. Additionally, Speiser, et al. U.S. Pat. No. 3,065,366 discloses pulse generator for controlling electrical equipment in which a piston-shaped permanent magnet which generates an electrical pulse in the output terminals of a coil as the magnetic flux through the coil is varied by moving the piston-shaped magnet passed the coil, and a free-piston generator of electric current in which the free piston has annular magnet on its periphery and in which the cylinder has annular grooves formed in its inside wall containing a nonmagnetic material such as a ceramic or epoxy is known from U.S. Pat. No. 3,105,153.
However, none of these patents disclose an arrangement which represents a practical approach for the generation of electrical power during reciprocation of the piston of an engine which allow powering of a telemetry package mounted on the engine piston for obtaining data concerning conditions at the piston during engine operation, nor can they be installed into an otherwise stock engine without requiring major modifications.
Thus, a need exists for a piston-mounted power generator suitable for engine piston telemetry systems which will enable in-cylinder measurements of strain, temperature, vibration, etc., to be obtained more extensively and effectively without requiring major structural changes to the engine, at idling speeds in addition to high operating speeds and for extended periods of time.